Freshwater Locations Research Articles

Spatial distribution and circadian locomotor activity of invasive armored catfish (Loricariidae) in the freshwater and brackish water.

Invasive suckermouth armored catfish Pterygoplichthys spp. successfully spread during one decade into many river systems of Vietnam. Wide and rapid invasion of armored catfish might be associated with using brackish water in estuaries to spread from one river system to another. The first goal of our study was to assess the horizontal and vertical distribution of invasive fish in freshwater (Da Rang River) and in brackish water (Da Rang River estuary) associated with circadian rhythm. In the both sampling locations, fish were mainly caught at nighttime at the bottom and near the surface using the net traps and vertical nets. In estuary, fish were caught in the net traps with distance 2.0-7.5 m from the right or left banks where water was predominantly fresh. In freshwater of the Da Rang River, fish were often caught near the left bank with gravel and stone substrate. The second goal of our study was to experimentally evaluate the circadian (12 hours of the night and 12 hours of the day) rhythm of locomotor activity (LA) of fish. Fish from different freshwater locations (Am Chua canal and Da Rang River) had a similar diurnal dynamic of LA with mostly movements (77-83% of total diurnal LA) at nighttime (18:00-6:00, GMT+7) at the end of the wet season. Armored catfish from the brackish water location (Da Rang River estuary) also were mostly active (76% of total diurnal LA) overnight. However, fish from freshwater and brackish water had difference in the timing of behavioral activity. Fish LA from estuary was significantly lower than LA of fish from freshwater locations during 18:00 to 21:00 before low tide. The results of our field and experimental studies established that armored catfish in estuary moved in horizontal and vertical planes predominantly at nighttime. Tide level regulates locomotor activity of invasive fish and could influence on the possibility of their spreading through the estuary.

Distribution and ecology of the generalist lactic acid bacterium Carnobacterium maltaromaticum in different freshwater habitats: Metabolic and antagonistic abilities.

We explored the distribution, metabolic and antagonistic activities of Carnobacterium maltaromaticum, isolated from freshwater locations in Denmark during winter or early spring. This species was widely distributed in such habitats although it was relatively rare in low pH locations. Isolates possessed a diverse metabolism, potentially enabling functional capacities independent of habitat. The intraspecies competition showed a relatively high degree of mostly low-intensity interactions, which overall were not correlated with phylogeny or location. Only a few isolates exhibited broad-spectrum inhibition activity, targeting species from other genera and families, including one isolate that exhibited a broad inhibitory activity due to H2 O2 production. Bioinformatic analyses revealed that the frequency of bacteriocinogenic systems was low, and only one unmodified bacteriocin, piscicolin 126, correlated with phenotypic antagonistic activity. Furthermore, most potential bacteriocin gene complexes were not complete. Overall, this study showed C. maltaromaticum to be a generalist (nomadic) species with a constant presence in freshwater habitats, especially those with pH values >5. General metabolic properties did not suggest a strong degree of adaptation to the freshwater environment, and bacteriocin-mediated antagonistic activities appeared to play a minimal ecological role.

Factors affecting the micronutrient status of adolescent girls living in complex agro-aquatic ecological zones of Bangladesh

Inadequate intake of both macro and micronutrients is the major determinant of micronutrient deficiencies in adolescent girls. This study assessed multiple micronutrient status including vitamin D, iron, vitamin A, and urinary iodine concentration among adolescent girls through two seasonal cross-sectional surveys conducted during dry and wet seasons. Mixed-effects linear and logistic regression analysis were conducted to assess associations between micronutrient status, salinity and seasonality. The mean age of the girls was 14 years. Vitamin (OH)D insufficiency was significantly higher in freshwater areas in wet season compared to dry season (wet season: 58% and dry season: 30%, P < 0.001). In wet season, risk of vitamin (OH)D insufficiency was three times higher compared to dry season (AOR: 3.03, 95% CI 1.71, 5.37, P < 0.001). The odds of vitamin (OH)D insufficiency was 11 times higher in fresh water areas compared to high saline areas (AOR: 11.51, 95% CI 3.40, 38.93, P < 0.001). The girls had higher risk of iron deficiency in wet season. Despite the environment being enriched with micronutrient-contained aquatic food, adolescent girls in coastal areas experience different micronutrient deficiencies. The high prevalence of vitamin (OH)D insufficiency in freshwater locations and seasonal iron deficiency in high saline areas needs attention.

Responses of Phytoplankton Benthic Propagules to Macronutrient Enrichment and Varying Light Intensities: Elucidation from Monsoon-Influenced Mandovi and Zuari Riverine System : Responses of Phytoplankton Benthic Propagules to Macronutrient Enrichment and Varying Light Intensities: Elucidation from Monsoon-Influenced Mandovi and Zuari Riverine System.

The ecological importance of phytoplankton-benthic-propagules (PBP) from coastal sediments, except tropical monsoon-influenced rivers and estuaries, is well documented. PBP in such systems is often transported from upstream (near freshwater) to downstream (estuary) through freshwater discharges during monsoon and thereby experiences higher salinities (>30 PSU) and nutrients with varying light conditions due to reducing discharges during the monsoon-break/withdrawal-phase. However, the PBP responses (germination and subsequent growth) to such changes are unknown and are examined here at ~35 PSU salinity. For the study, macronutrients (nitrate, phosphate, silicate, and nitrate+phosphate+silicate) and light intensities were considered to assess the response of PBP representing estuarine, brackish, and near freshwater locations of monsoon-influenced Mandovi and Zuari rivers (Goa, India). Diatoms dominated the viable PBP community, but the maximum growth and sustained photosynthetic activity were observed when all macronutrients were supplied than individually. Here, variable fluorescence technique utility in PBP resurrection (detection of viability and responses) was also explored. The PBP growth was similar for macronutrients but increased with light intensity indicating a longer growth response during monsoon. For PBP (germination and photosynthetic activity), light intensities drive the rate of improvement/development, whereas the nutrients are essential for maintaining vegetative growth upon germination in the region. The PBP dominance of common planktonic species (Skeletonema and Thalassiosira) along the river also signifies the role of seawater intrusion (up to upstream locations) in distribution. Skeletonema and Thalassiosira, which contribute significantly to the total community, are light-sensitive with a similar response and cause single species blooms during monsoon and non-monsoon, respectively, depending on the species' tolerance to salinity.

Reproductive strategy of Delta Smelt Hypomesus transpacificus and impacts of drought on reproductive performance.

Understanding reproductive biology and performance of fish is essential to formulate effective conservation and management programs. Here, we studied reproductive strategies of female Delta Smelt Hypomesus transpacificus, an endangered fish species in the State of California, the United States, focusing on (1) better understanding their distribution pattern during the winter and spring spawning season at very fine scale to predict their possible spawning grounds and (2) assessing impacts of a recent, severe drought on their reproductive performance. We formulated our hypotheses as follows; (1) female Delta Smelt migrate to particular locations for spawning so that mature females can be frequently found in those locations throughout the spawning season and (2) reproductive performance of individual female fish declined during the drought. To test the first hypotheses, we analyzed relationships between water quality parameters and maturity/distribution pattern of Delta Smelt. Salinity better explained the distribution pattern of Delta Smelt at subadult and adult stages compared with water temperature or turbidity. Although there are some freshwater locations where mature Delta Smelt can frequently be found during the spawning season, Delta Smelt at the final maturation stage (Stage 5: hydration) and post spawners appeared to be widespread in the area where salinity was below 1.0 during the spawning season. Therefore, Delta Smelt could theoretically spawn in any freshwater locations, with more specific spawning requirements in the wild (e.g., substrate type and depth) still unknown. Delta Smelt, which experienced dry and critically dry conditions (the 2013 and 2014 year-classes), showed smaller oocytes, and lower clutch size and gonadosomatic index compared with the fish caught in a wet year (2011 year-class) at the late vitellogenic stage (Stage 4 Late), suggesting reproductive performance was negatively affected by environmental conditions during the drought.

Genetic structure and origin of non-native, free-living Atlantic salmon Salmo salar along a latitudinal gradient in Chile, South America

Limited stocking efforts to introduce Atlantic salmon Salmo salar into Chilean rivers and streams were unsuccessful during the 20th century. Following the arrival of the aquaculture industry during the 1980s, escaped Atlantic salmon have presented an ecological risk to native taxa through predation, competition, and transmission of pathogens or parasites. However, whether commercial aquaculture strains represent the likely source of free-living Atlantic salmon in marine and freshwater environments is unclear. We used 272 single nucleotide polymorphisms to characterize free-living Atlantic salmon (n = 80) captured from 12 marine and freshwater locations in southern Chile. These were compared with 8 reference collections, 6 known commercial strains, and 2 wild populations of Atlantic salmon. We evaluated genetic structure among free-living Atlantic salmon and assessed individual ancestry and origin by assigning mixture samples to reference collections. We found evidence for genetic structure (number of clusters, K = 3) among free-living salmon unexplained by geography, environment, or life stage, but consistent with the number of clusters among commercial aquaculture strains. Most free-living Atlantic salmon had a close ancestry with farmed Norwegian strains, the most widely used by the industry, pointing to recent aquaculture escapes as their origin. Yet recent establishment of self-sustaining populations weakly differentiated from aquaculture broodstock cannot be ruled out. We propose increasing monitoring efforts of free-living Atlantic salmon in remote sites as well as in watersheds located in densely stocked aquaculture areas.

New Dothideomycetes from Freshwater Habitats in Spain.

The Dothideomycetes are a class of cosmopolitan fungi that are present principally in terrestrial environments, but which have also been found in freshwater and marine habitats. In the present study, more than a hundred samples of plant debris were collected from various freshwater locations in Spain. Its incubation in wet chambers allowed us to detect and to isolate in pure culture numerous fungi producing asexual reproductive fruiting bodies (conidiomata). Thanks to a morphological comparison and to a phylogenetic analysis that combined the internal transcribed spacer (ITS) region of the nrDNA with fragments of the RNA polymerase II subunit 2 (rpb2), beta tubulin (tub2), and the translation elongation factor 1-alpha (tef-1) genes, six of those strains were identified as new species to science. Three belong to the family Didymellaceae: Didymella brevipilosa, Heterophoma polypusiformis and Paraboeremia clausa; and three belong to the family Phaeosphaeriaceae: Paraphoma aquatica, Phaeosphaeria fructigena and Xenophoma microspora. The finding of these new taxa significantly increases the number of the coelomycetous fungi that have been described from freshwater habitats.

The population genomics of repeated freshwater colonizations by Gulf pipefish.

How organisms adapt to the novel challenges imposed by the colonization of a new habitat has long been a central question in evolutionary biology. When multiple populations of the same species independently adapt to similar environmental challenges, the question becomes whether the populations have arrived at their adaptations through the same genetic mechanisms. In recent years, genetic techniques have been used to tackle these questions by investigating the genome-level changes underlying local adaptation. Here, we present a genomic analysis of colonization of freshwater habitats by a primarily marine fish, the Gulf pipefish (Syngnathus scovelli). We sample pipefish from four geographically distinct freshwater locations and use double-digest restriction site associated DNA sequencing to compare them to 12 previously studied saltwater populations. The two most geographically distant and isolated freshwater populations are the most genetically distinct, although demographic analysis suggests that these populations are experiencing ongoing migration with their saltwater neighbours. Additionally, outlier regions were found genome-wide, showing parallelism across ecotype pairs. We conclude that these multiple freshwater colonizations involve similar genomic regions, despite the large geographical distances and different underlying mechanisms. These similar patterns are probably facilitated by the interacting effects of intrinsic barriers, gene flow among populations and ecological selection in the Gulf pipefish.

Sex ratio and reproduction of invasive red devil, (Amphilophus labiatus: Cichlidae) in Lake Sentani, Indonesia

AbstractThe Red Devil Cichlid Amphilophus labiatus (Günther 1864), native to Lake Nicaragua and Lake Managua in Central America, is widely cultivated as an attractive, yet aggressive, aquarium fish that has been introduced to several freshwater locations around the world. It was recently introduced into Lake Sentani in Indonesian New Guinea, a naturally rich aquatic habitat home exhibiting a diverse fauna with high endemism. To better understand the invasive potential and impacts of A. labiatus, the present study was undertaken to describe the sex ratio and reproductive potential of A. labiatus in Lake Sentani through determination of its gonad maturation stages, gonado‐somatic index and fecundity. The fish were collected using floating gill nets at six locations around the lake between June and August 2019. Sex identification, gonads type, gonad stage and weight, fecundity were observed in the laboratory. Of the total 542 of A. labiatus collected during the survey, 345 individuals were sampled for sex ratio and reproduction. The overall male:female ratio was skewed towards males in a ratio of 3.28:1. The males were generally found to be in the gonad maturation stage I, while the females were commonly found in gonad maturation stages III and IV for all sampling locations during the study period. The highest male mean GSI value was found for the Yakonde site (0.24 ± 0.21) and at the Ayapo site (1.11 ± 1.01) for the females, with a fecundity of 191–2,720 eggs. The fish have spread to most parts of the lake, being conditioned to potentially spawn at any location, thereby providing an explanation for the observed rapid increase of the A. labiatus population over the last ten years. The results of the present study suggest a high invasive potential for this species in this and other similar lake habitats, warning that their careful management should be undertaken to restrict their further spread in Indonesia and elsewhere.

Migratory diversity in an Arctic fish supporting subsistence harvest

Arctic regions are warming more than twice as quickly as other parts of the globe, threatening Arctic fish and wildlife and the human communities that rely on them. Assessing species' vulnerability to this change requires understanding their life histories and ecology, including movement patterns and habitat use. However, this information has not been documented for many Arctic species, which may not follow predicable movements in these vast and changing landscapes. In the Gwich'in Settlement Area of western Canadian Arctic, one such species is łuk dagaii (in Gwich'in) or broad whitefish (Coregonus nasus). This species is the most important food fish for the Gwich'in Peoples of the region. We present results from a collaborative community-based research program established to build research capacity and address pressing research questions. Using otoliths extracted from fish caught by community monitors along the Peel River, we investigated migratory patterns using the isotopic ratio, 87Sr/86Sr. Applying a hidden Markov model to the otolith laser ablation transects, we explored emergent model states and linked them to regions of the watershed. Across and within individuals, fish occupied the ocean and three different identified freshwater locations; however, while all fish were captured in the Peel River, none expressed an otolith signature that would suggest they grew there. Across individuals, we found large variability in migratory patterns, suggesting that migrations are not obligate and that individual fish utilize the watershed very differently. This diversity may buffer whitefish and reliant human communities against change, but indicates dependence on a large, intact watershed.

A Regional Difference Analysis of Microplastic Pollution in Global Freshwater Bodies Based on a Regression Model

Based on statistical data of the average abundance of microplastics from 37 global freshwater locations up to November 2019, we classified the freshwater bodies according to developments in their local countries and geographic positions. We highlighted the differences and causes of microplastic pollution in the waters of both developed and developing countries and urban and rural areas. The results showed that microplastic pollution was highest in Asia. The pollution in developed countries was significantly lower than in developing countries. The differences in freshwater pollution between urban and rural areas mainly depended on the extent of human activity. The present study found the following phenomena by comprehensively using simple and multiple regression models and a Pearson correlation analysis to solve the impacts of the features, natural factors, and social and economic factors on the distribution of microplastic pollution. The density of microplastics was higher, which promoted the aggregation of microplastics in sediments. Pursuant to that, microplastic pollution was also influenced by the space-time pollution of movable surface sources, such as the soil and air. A population increase and the average gross domestic product (GDP) could also worsen microplastic pollution.

Interlaboratory accuracy and precision among results of three sewage-associated marker genes in urban environmental estuarine waters and freshwater streams

The application of quantitative polymerase chain reaction (qPCR) based microbial source tracking (MST) marker genes are increasingly being used to identify contaminating sources and inform management decisions. In this study, we assessed interlaboratory agreement on duplicate environmental water samples collected from estuarine and freshwater locations, by comparing results of qPCR based testing for Bacteroides HF183, crAssphage CPQ_056, and pepper mild mottle virus (PMMoV). The overall agreements (co-detection and non-co-detection) between CSIRO Land and Water (CLW) laboratory and Sydney Water (SW) laboratory for the HF183, crAssphage CPQ_056 and PMMoV marker genes for duplicate water samples were 74, 75 and 74%, respectively. Cohene's kappa (k) revealed fair to moderate agreements and acceptable relative percent difference (RPD) values of <15% for duplicate samples. The pooled mean abundances of HF183, CPQ_056, and PMMoV in measurable samples at the CLW laboratory were 5.19 ± 0.93, 5.12 ± 0.82, and 4.42 ± 0.65 log10 copies/L, respectively. However, the pooled mean abundances were significantly lower at the SW laboratory, HF183 (4.58 ± 0.84 log10 copies/L), crAssphage CPQ_056 (4.20 ± 0.63 log10 copies/L), and PMMoV (3.89 ± 0.41 log10 copies/L). At individual sample level, most of the paired samples had <1 log10 difference. Significant positive Spearman rank correlations were obtained between two laboratories for the HF183 (Rs = 0.65; p < 0.05), CPQ_056 (Rs = 0.79; p < 0.05), and PMMoV (Rs = 0.54; p < 0.05) marker genes. Several factors such as standards, qPCR platforms, PCR inhibitors, nucleic acid extraction efficiency and low levels of targets in some samples may have contributed to the observed discrepancies. Results presented in this study highlight the importance of standardized protocol, laboratory equipment (such as digital PCR), sample processing strategies and appropriate quality controls that may need implementation to further improve accuracy and precision of results between laboratories.

&lt;p&gt;&lt;strong&gt;Catalogue of Croatian Freshwater Rhodophytes&lt;/strong&gt;&lt;/p&gt;

This paper summarises all available data on the flora of freshwater rhodophytes in Croatia, comprising 18 species from 13 genera—Audouinella, Bangia, Batrachospermum, Chroodactylon, Compsopogon, Hildenbrandia, Lemanea, Paralemanea, Pneophyllum, Polysiphonia, Porphyridium, Sirodotia and Thorea. Presented data are mostly a result of a comprehensive survey undertaken from 2009 to 2019 and including more than 600 freshwater locations—channels, streams, rivers, natural and artificial lakes. Additionally, all available published historical data, dating from 1890 onwards, as well as herbarium material from the ZA collection was overviewed and included in this study.

Occurrence and spatial distribution of organochlorine pesticides in the southwest Buenos Aires using the freshwater snail Chilina parchappii as environmental biomonitor

Organochlorine pesticides are highly toxic compounds for biota and humans that have been used for sanitary and phytosanitary purposes for many years in Argentina and the world due to their low cost and versatility. Despite a worldwide ban in the 1970s and 1980s, Argentina banned their use and production by the 1990s and in particular endosulfan during 2013. In the present research 1300 Chilina parchappii individuals – a wild native snail – were collected from eight freshwater locations in the Buenos Aires Province southwest, Argentina, in a period between April–May 2017, to assess the concentration levels, spatial distribution and putative input sources of 16 selected organochlorine pesticides (OCs) including endosulfan. Average concentration in snails ranged between 2.59 and 6.46 ng.g−1, dry weight (dw) (mean = 4.27 ng.g−1, dw), for ∑OCs, and from lower detection limit (<LD) to 1.21 ng.g−1, dw. (mean = 0.53 ng.g−1, dw), and from 0.39 to 5.25 ng.g−1 (mean = 1.20 ng.g−1, d.w.) for ∑HCHs and ∑DDXs, respectively. ∑Endosulfans ranged from <LD to 4.36 and accounted for 45% of the total OCs burden at the area. The general order of abundance was as follow: β endosulfan> 4,4-DDE> heptachlor exo-epoxide (isomer B)> aldrin>γ HCH>δ HCH> dieldrin>α HCH> 4,4- DDD>α endosulfan> endosulfan sulfate> 4,4-DDT>β HCH> heptachlor> endrin aldehyde> endrin.The principal component analysis allowed the classification of sampling sites according to the main OCs inputs over the area. In comparison to other worldwide freshwater bioindicators, Chilina parchappii DDXs and HCHs levels were in the low range; on the opposite, ∑OCs average was in the medium range.Data indicated that Chilina parchappii is accumulating OCs from the surrounding media (either in use or banned) setting a present alert for the endosulfan environmental burden.

DNA Barcoding: A Study of Guppy Fish (Poecilia reticulata) in East Java, Indonesia

Poecilia reticulata is a freshwater fish from the northeastern part of South America and spread widely to various countries in Asia and other continents. However, research about P. reticulate is limited even though it is a well-known fish species in Indonesia. The purpose of study was to identify the fish species of P. reticulata through DNA barcoding using the COI gene to determine the phylogenetic relationships among fish populations in East Java, Indonesia. In a present study, there were eight samples of P. reticulata from four different freshwater locations in East Java. Extraction, amplification, and sequencing of DNA samples were conducted to obtain the genetic data and construct a phylogenetic tree based on DNA sequences. The COI gene is the most popular markers to study genetic populations and phylogeography among the animal kingdom. Our phylogenetic reconstruction showed a clear that there were two groups of P. reticulata. The first group was obtain through species from East Java, Sukabumi, West Java (KU692776.1), Dominican Republic, Pandeglang, Banten and Myanmar. The second group was P. reticulata from southern Africa, Brazil, and Sukabumi, West Java (KU692775.1). The result of this study indicate that the guppy fish in East Java identic with P. reticulata from West Java (KU692776.1), which a widely used in classification based on evolutionary relationships. The findings of this study have important implication for the development of advance research about adaptation, phylogeny, and evolution of fish, especially of guppy fish.

Alanine, proline and urea are major organic osmolytes in the snail Theodoxus fluviatilis under hyperosmotic stress.

Hyperosmotic stress may result in osmotic volume loss from the body to the environment in animals that cannot control the water permeability of their integument. Euryhaline animals (which have a wide tolerance range of environmental salinities) have generally evolved the ability to counteract cell volume shrinkage by accumulating inorganic and organic osmolytes within their cells to balance internal and external osmolalities. Molluscs use very different combinations of amino acids and amino acid derivatives to achieve this goal. Theodoxus fluviatilis is a neritid gastropod that is distributed not only in limnic habitats in Europe but also in brackish waters (e.g. along the shoreline of the Baltic Sea). Animals from brackish sites survive better in high salinities than animals from freshwater locations. The results of the present study indicate that these differences in salinity tolerance cannot be explained by differences in the general ability to accumulate amino acids as organic osmolytes. Although there may be differences in the metabolic pathways involved in osmolyte accumulation in foot muscle tissue, the two groups of animals accumulate amino acid mixtures equally well when stepwise acclimated to their respective maximum tolerable salinity for extended periods. Among these amino acids, alanine and proline, as well as the osmolyte urea, hold a special importance for cell volume preservation in T. fluviatilis under hyperosmotic stress. It is possible that the accumulation of various amino acids during hyperosmotic stress occurs via hydrolysis of storage proteins, while alanine and proline are probably newly synthesised under conditions of hyperosmotic stress in the animals.

Transient bottom water oxygenation creates a niche for cable bacteria in long-term anoxic sediments of the Eastern Gotland Basin.

Cable bacteria have been reported in sediments from marine and freshwater locations, but the environmental factors that regulate their growth in natural settings are not well understood. Most prominently, the physiological limit of cable bacteria in terms of oxygen availability remains poorly constrained. In this study, we investigated the presence, activity and diversity of cable bacteria in relation to a natural gradient in bottom water oxygenation in a depth transect of the Eastern Gotland Basin (Baltic Sea). Cable bacteria were identified by FISH at the oxic and transiently oxic sites, but not at the permanently anoxic site. Three species of the candidate genus Electrothrix, i.e. marina, aarhusiensis and communis were found coexisting within one site. The highest filament density (33 m cm-2 ) was associated with a 6.3 mm wide zone depleted in both oxygen and free sulphide, and the presence of an electric field resulting from the electrogenic sulphur oxidizing metabolism of cable bacteria. However, the measured filament densities and metabolic activities remained low overall, suggesting a limited impact of cable bacteria at the basin level. The observed bottom water oxygen levels (< 5 μM) are the lowest so far reported for cable bacteria, thus expanding their known environmental distribution.

Influence of Darkness and Aging on Marine and Freshwater Biofilm Microbial Communities Using Microcosm Experiments.

Ballast tank biofilms pose an additional risk of microbial invasion if sloughed off during ballasting operations, yet their significance and invasion biology is poorly understood. In this study, biofilms developed in marine and freshwater locations were exposed to prolonged darkness and aging by mimicking ballast water conditions in the laboratory. Upon prolonged darkness, the decay of phytoplankton, as indicated by the decrease in chlorophyll a in marine biofilms, led to remineralization and enhanced bacterial and protist populations. However, the same trend was not observed in the case of freshwater biofilms wherein the microbial parameters (i.e., bacteria, protists) and chlorophyll a decreased drastically. The bacterial community structure in such conditions was evaluated by real-time quantitative PCR (qPCR), and results showed that the biofilm bacterial communities changed significantly over a period of time. α-Proteobacteria was the most stable taxonomic group in the marine biofilms under dark conditions. However, β-proteobacteria dominated the freshwater biofilms and seemed to play an important role in organic matter remineralization. γ-Proteobacteria, which includes most of the pathogenic genera, were affected significantly and decreased in both the types of biofilms. This study revealed that marine biofilm communities were able to adapt better to the dark conditions while freshwater biofilm communities collapsed. Adaptation of tolerant bacterial communities, regeneration of nutrients via cell lysis, and presence of grazers appeared to be key factors for survival upon prolonged darkness. However, the fate of biofilm communities upon discharge in the new environment and their invasion potential is an important topic for future investigation.

The Impact of Salts on Single Chain Amphiphile Membranes and Implications for the Location of the Origin of Life.

One of the key steps in the origins of life was the formation of a membrane to separate protocells from their environment. These membranes are proposed to have been formed out of single chain amphiphiles, which are less stable than the dialkyl lipids used to form modern membranes. This lack of stability, specifically for decanoate, is often used to refute ocean locations for the origins of life. This review addresses the formation of membranes in hydrothermal-vent like conditions, as well as other environmental constraints. Specifically, single chain amphiphiles can form membranes at high sea salt concentrations (150 g/L), high temperatures (65 °C), and a wide pH range (2 to 10). It additionally discusses the major challenges and advantages of membrane formation in both ocean and fresh water locations.

Abiotic factors affecting habitat selection by two invasive gammarids Dikerogammarus villosus and Pontogammarus robustoides

Identification of habitat preferences of invasive organisms is crucial for predicting their distribution and impact. We conducted laboratory experiments to determine preferences of Dikerogammarus villosus and Pontogammarus robustoides, invasive in Europe, with regard to ionic content (450 and 830 μS/cm in a Y-maze), flow (0–30 cm/s in a flow-through tank with stagnant water refuges) and temperature (a gradient 5–35°C). D. villosus selected the lower salinity, whereas P. robustoides did not discriminate between salinities, suggesting that, the raised ionic content in large European rivers cannot explain their absence in small tributaries, as previously postulated. Gammarids never preferred flowing over stagnant water, but could stay in a flow ≤10 cm/s without behavioural changes. They avoided flow ≥15 cm/s. Gammarids selected warmer water than their acclimation temperatures. Temperature selection by D. villosus was related to its acclimation temperature. The choice of P. robustoides depended on the season: it preferred a lower temperature in summer than in autumn. Therefore, its thermal preferences were more stable throughout the year, which might be advantageous in shallow, thermally variable areas. Gammarids used environmental variables to select warm, lentic, freshwater locations, which may help them locate an optimum microhabitat and thrive in temporally and spatially variable environments.